1. Field of the Invention
The present invention relates to an optical navigation chip, and in particular to an optical navigation chip appropriate for an optical pointing device.
2. Description of the Related Art
A mouse is a commonly used input device. A wheel mouse processes a displacement signal, a button signal, and an interface signal and communicates with a computer via a PS2 interface, a universal serial bus (USB) interface, or a wireless communication interface using the mechanical structure of its wheel and a micro-controller chip. An optical mouse replaces the mechanical structure of the wheel mouse with a complementary metal oxide semiconductor (CMOS) photo sensor chip capable of optical navigation. Capable of digital signal processing (DSP), the CMOS photo sensor chip is able to integrate with the functionality of the micro-controller chip of the wheel mouse, thus becoming a system-on-chip (SoC) chip offering reduced cost and power consumption.
Moreover, the CMOS photo sensor chip calculates a correlation between images captured at different times for determining a displacement of the optical mouse. Therefore, the quality of images can influence the calculation result. The quality of images is affected by environmental noise, focus errors, and un-uniform light sources. Thus, an additional circuit is necessary on the SoC chip for determining quality of the images.